This invention relates to diaphragm valves, and more particularly to diaphragm valves which are designed to mount to tank bottoms of sterile vessels.
Similar devices include ball valves, quarter turn valves which have a ported sphere and a pair of seats in a housing. When open, fluid flows from one end of the valve through the ball and out the other end. Rotating the ball 90 degrees closes the valve and prevents fluid flow. The ball may be fixed or floating Plunger valves are linear motion valves which create a seal by forcing an elastomeric boot into a seat area. When the valve opens, the boot convolutes on itself to provide fluid flow. A ram valve is a linear motion valve which consists of a spindle/ piston combination. The seal is typically metal to metal. Another linear motion valve similar to a ram valve is the kettle valve, but a molded elastomer seal, mushroom shaped, is on the end of the shaft.
The foregoing valves are not ideally suited to process fluids in the pharmaceutical/bioprocessing industries. These valves have many limitations including too large in size, they generate a large sump at the vessel bottom and generate crevices in which bacteria can grow, they trap fluid in ball cavity which requires cavity fillers and steam ports to clean, they have poor interior finish and have non-streamlined fluid passages, they do not isolate the working parts from the line fluid, they do not provide positive closure and are not autoclavable, and they contain welds, i.e. mounting flange is normally welded to valve body.
The state of the art of diaphragm valves are known from the following U.S. Pat. Nos.:
______________________________________ 1,497,275 3,250,511 2,186,833 3,349,795 2,605,991 3,623,700 2,616,164 3,628,770 2,725,211 3,631,882 2,892,613 4,505,451 3,134,286 4,596,268 3,134,571 ______________________________________
The state of the art for valves used in connection tanks are known from the following U.S. Pat. Nos.:
2,679,860 PA0 3,665,946 PA0 3,895,651 PA0 3,918,678 PA0 4,836,236
The tank bottom diaphragm valve according to the invention overcomes the above problems by employing the inherent design features of the diaphragm valves which include positive closure, zero pockets, minimal contact surfaces, streamlined fluid passage, bonnet isolation, and ease of maintenance. The tank bottom diaphragm valve of the invention provides a clean, totally drainable means to isolate the vessel from downstream process piping, and the overall dimensional envelope is minimal and all materials of construction are FDA compliant and autoclavable.